Determination of the mechanical properties of manufactured articles is useful for predicting the performance and applications of new articles and compositions as well as ensuring consistent quality of existing processes and/or articles of manufacture. One such property that can be evaluated is the modulus of elasticity (e.g., Young' modulus, elastic modulus). The modulus of elasticity is a measure of a material's relative stiffness, or more specifically, a measure of the rate of change in stress with respect to strain.
One method of determining the modulus of elasticity (E) for a composition or article is through tensile testing. Tensile testing first comprises securing a sample of known dimensions between an upper moving jaw and a bottom stationary jaw, which are disposed at a known distance therebetween. Once secured, the upper jaw can advance in a direction away from the bottom jaw, which generates a tensile force on the test article. The resulting stress is plotted with respect to the strain generated, wherein the modulus of elasticity is equal to the slope of the graph. This principle is illustrated in equation (I) below;
      E    =                  stress        strain            =                        (                      F            A                    )                          (                      d            l                    )                          Wherein    ;                                E          =                      Modulus            ⁢                                                  ⁢            of            ⁢                                                  ⁢            Elasticity                                                        F          =                      Measured            ⁢                                                  ⁢            Force                                                        A          =          Area                                              d          =                      Extension            ⁢                                                  ⁢            Length                                                        l          =                      Original            ⁢                                                  ⁢            Length                              
Although tensile testing can be utilized to calculate the modulus of elasticity for an article, the test is destructive, which can present manufacturers with a loss in profit. Furthermore, tensile testing cannot predict changes in the modulus of elasticity across an article; rather, tensile testing is a measurement of the article's gross properties.
As a result, manufacturers desire a method for testing the mechanical properties of articles without the need for destructive mechanical testing, and further desire a test method that comprises the fidelity to determine the modulus of elasticity across an entire surface of the article.